1. Field of the Invention
The present invention relates to a thermal printer, and particularly to a thermal printer using recording papers of different width-sizes.
2. Description of the Related Art
There is a color thermal printer in which a color thermosensitive recording paper is advanced, and during advancement thereof, a thermal head is pressed against the recording paper to print a full-color image by activating a heating-element array. The thermal head is pressed against the recording paper in order to properly apply the heat of the heating-element array to the recording paper. If a pressure force for pressing the thermal head is weak, the heat of the heating-element array is hard to transfer to the recording paper. Due to this, are caused defective prints in which a coloring density is paler than a desired density and a coloring area of a single pixel becomes small, for instance. Meanwhile, if the pressure force for pressing the thermal head is too strong, defective conveyance of the recording paper is caused.
The pressure force of the thermal head for the recording paper is determined in accordance with a width-size of the recording paper. For example, the pressure force of 0.05 Kg is applied to the recording paper per 1 mm thereof in a width direction. In a case that printing is performed on the recording paper having a width of 89 mm, it is necessary to press the thermal head against the recording paper with the pressure force of 4.45 Kg. In another case that printing is performed on the recording paper having a width of 102 mm, it is necessary to press the thermal head against the recording paper with the pressure force of 5.10 Kg.
Some of the color thermal printers can perform the printing on the color thermosensitive recording papers having different width-sizes. In the conventional color thermal printers, however, the pressure force of the thermal head is not changed after the width-size of the recording paper has changed. Thus, there arise problems in that defective prints and defective conveyance of the recording paper are caused.
In view of the foregoing, it is a primary object of the present invention to provide a thermal printer in which a thermal head is pressed against recording papers of different width-sizes with an appropriate force and at an appropriate position.
It is a second object of the present invention to provide a thermal printer in which defective prints and defective conveyance of a recording paper are prevented from occurring.
In order to achieve the above and other objects, the thermal printer according to the present invention comprises a head pressing mechanism by which a pressure force for pressing the thermal head against the recording paper is changed in accordance with a width of the used recording paper. Incidentally, pressure positions for pressing the thermal head may be also changed together with the pressure force by utilizing the head pressing mechanism.
In the thermal printer according to the present invention, it is possible to press the thermal head against the recording paper with the suitable pressure force and the suitable pressure positions in accordance with the width-size of the recording paper. Thus, printing and conveyance of the recording paper may be properly performed notwithstanding the change of the width-size of the recording paper to be used.